1. Field of the Invention
The present invention relates to a surface discharge type full color surface discharge type plasma display panel and a process for manufacturing the same. More specifically, the present invention relates to a full color ac plasma display device high in resolution and brightness of display such that it is adaptable to a high quality display, such as a high definition TV, and can be used in daylight.
2. Description of the Related Art
A plasma display panel (PDP) has been considered the most suitable flat display device for a large size, exceeding over 20 inches, because a high speed display is possible and a large size panel can easily be made. It is also considered to be adaptable to a high definition TV. Accordingly, an improvement in full color display capability in plasma display panels is desired.
In the past, two electrode type dc and ac plasma display panels have been proposed and developed. Also, a surface discharge type ac plasma display panel, among other plasma display panels, has been known to be suitable for a full color display.
For example, a surface discharge type ac plasma display panel having a three electrode structure comprises a plurality of parallel display electrode pairs formed on a substrate and a plurality of address electrodes perpendicular to the display electrode pairs for selectively illuminating unit luminescent areas. Phosphors are arranged, in order to avoid damage by ion bombardment, on the other substrate facing the display electrode pairs with a discharge space between the phosphor and the display electrode pairs and are excited by ultra-violet rays generated from a surface discharge between the display electrodes, thereby causing luminescence. See for example, U.S. Pat. No. 4,638,218 issued on Jan. 20, 1987 and U.S. Pat. No. 4,737,687 issued on Apr. 12, 1988.
The full color display is obtained using an adequate combination of three different colors, such as red (R), green (G) and blue (B), and an image element is defined by at least three luminescent areas corresponding to the above three colors.
Conventionally, an image element is composed of four subpixels arranged in two rows and two columns, including a first color luminescent area, for example, R, a second color luminescent area, for example, G, a third color luminescent area, for example, G, and a fourth color luminescent area, for example, B. Namely, this image element comprises four luminescent areas of a combination of three primary colors for additive mixture of colors and an additional green having a high relative luminous factor. By controlling the additional green area independent from the other three luminescent areas, an apparent image element number can be increased and thus an apparent higher resolution or finer image can be obtained.
In this arrangement of four subpixels, two pairs of display electrodes cross an image element, i.e., each pair of display electrodes crosses each row or column of subpixels, which is apparently disadvantageous in making image elements finer.
If the image elements are to be finer, formation of finer display electrodes becomes difficult and the drive voltage margin for avoiding interference of discharge between different electrode lines becomes narrow. Moreover, the display electrodes become narrower, which may cause damage to the electrodes. Further, a display of one image element requires time for scanning two lines, which may make a high speed display operation difficult because of the frequency limitation of a drive circuit.
The present invention is directed to solve the above problem and provide a flat panel full color surface discharge type plasma display device having fine image elements.
JP-A-01-304638, published on Dec. 8, 1989, discloses a plasma display panel in which a plurality of parallel barriers are arranged on a substrate and luminescent areas, in the form of strips defined by the parallel barriers, are formed. This disclosure is, however, directed only to two electrode type plasma display panels, not to a three electrode type plasma display panel in which parallel display electrode pairs and address electrodes intersecting the display electrode pairs are arranged and three luminescent areas are arranged in the direction of the extending lines of the display electrode pairs as in the present invention.
The present invention is also directed to a plasma display panel exhibiting a high image brightness at a wide view angle range. In this connection, U.S. Pat. No. 5,086,297 issued on Feb. 4, 1992, corresponding to JP-A-01-313837 published on Dec. 19, 1989, discloses a plasma display panel in which phosphors are coated on side walls of barriers. Nevertheless, in this plasma display panel, the phosphors are coated selectively on the side walls of barriers and do not cover the flat surface of the substrate on which electrodes are disposed.
To attain the above and other objects of the present invention, there is provided a full color surface discharge type plasma display device comprising pairs of lines of display electrodes (X and Y), each pair of lines of display electrodes being parallel to each other and constituting an electrode pair for surface discharge; lines of address electrodes (22 or A) insulated from the display electrodes and running in a direction intersecting the lines of display electrodes; three phosphor layers (28R, 28G and 28B), different from each other in respective luminescent colors, facing the display electrodes and arranged in a successive order of the three phosphor layers along the extending lines of the display electrodes, and a discharge gas in a space (30) between said display electrodes and said phosphor layers, wherein the adjacent three phosphor layers (28R, 28G and 28B) (EU) of said three different luminescent colors and a pair of lines of display electrodes define one image element (EG) of a full color display.
In accordance with the present invention, there is also provided a full color surface discharge plasma display device comprising first and second substrates facing and parallel to each other for defining a space in which a discharge gas is filled; pairs of lines of display electrodes formed on the first substrate facing the second substrate, each pair of lines of display electrodes being parallel to each other and constituting an electrode pair for surface discharge; a dielectric layer over the display electrodes and the first substrate; lines of address electrodes formed on the second substrate facing the first substrate and running in a direction intersecting the lines of display electrodes; three phosphor layers, different from each other in respective luminescent colors, formed on the second substrate in a successive order of said three luminescent colors along the extending lines of the display electrodes, the phosphor layers entirely covering the address electrodes; and barriers standing on the second substrate to divide and separate said discharge space into cells corresponding to respective phosphor layers, the barriers having side walls; wherein the adjacent three phosphor layers of said three different luminescent colors and a pair of lines of display electrodes define one image element of a full color display and said phosphor layers extend to the side walls of said barriers to cover almost the entire surfaces of the side walls of said barriers.
In accordance with a preferred embodiment of the present invention, there is provided a full color surface discharge plasma display device comprising first and second substrates facing and parallel to each other for defining a space in which a discharge gas is filled, the first substrate being disposed on a side of a viewer; pairs of to lines of display electrodes formed on the first substrate facing the second substrate, each pair of lines of display electrodes being parallel to each other and constituting an electrode pair for surface discharge, each of the display electrodes comprising a combination of a transparent conductor line and a metal line in contact with said transparent conductor line and having a width narrower than that of the transparent conductor line; a dielectric layer over the display electrodes and the first substrate; lines of address electrodes formed on the second substrate facing the first substrate and running in a direction intersecting the lines of display electrodes; barriers standing on the second substrate, in parallel to said address electrodes, for dividing said discharge gas space into cells, the barriers having side walls; and three phosphor layers, different from each other in respective luminescent colors formed on the second substrate in a successive order of said three luminescent colors along the extending lines of the display electrodes, the phosphor layers entirely covering the address electrodes and extending to the side walls of said barriers to cover almost the entire surfaces of the side walls of said barriers; wherein the adjacent three phosphor layers of said three different luminescent colors and a pair of lines of display electrodes define one image element of a full color display.
To protect the phosphor provided over the address electrode from ion bombardment, the following drive can be adopted. First, an erase address type drive control system in which once all image elements corresponding the pair of to the display electrodes are written, an erase pulse is applied to one of the pair of the display electrodes and simultaneously an electric field control pulse for neutralizing or cancelling the applied erase pulse is selectively applied to the address electrodes.
Second, a write address type drive control system is provided in which in displaying a line corresponding to a pair of the display electrodes, a discharge display pulse is applied to one of the pair of the display electrodes and simultaneously an electric field control pulse for writing is selectively applied to the address electrodes. This write address type drive control system is preferably constituted such that in displaying a line corresponding to a pair of the display electrodes, once all image elements corresponding to the display electrodes are subject to writing and erasing discharges, to store positive electric charges above said phosphor layers and negative electric charges above said insulating layer, an electric discharge display pulse is applied to one of the pair of the display electrodes to make said one of the pair of the display electrodes negative in electric potential to the other of the pair of the display electrodes, and an electric discharge pulse is selectively applied to the address electrodes to make the address electrodes positive in electric potential relatively to said one of the pair of the display electrodes.
It is preferred in the above full color surface discharge plasma display device that the image element has an almost square area and each of the three phosphor layers has a rectangular shape that is obtained by dividing the square of the image element and is long in a direction perpendicular to the lines of display electrodes. Additionally, it is preferred that each of the lines of the display electrodes comprises a combination of a transparent conductor line and a metal line in contact with the transparent conductor line and having a width narrower than that of the transparent conductor line and is disposed on the side of a viewer compared with the phosphor layers; the transparent conductor lines have partial cutouts in such a shape that the surface discharge is localized to a portion between the display electrodes without the cutout in each unit luminescent area; the total width of a pair of the display electrodes and a gap for discharge formed between the pair of the display electrodes is less than 70% of a pitch of the pairs of display electrodes; the device further comprises barriers standing on a substrate and dividing and separating the space between the display electrodes and the phosphor layers into cells corresponding to respective phosphor layers; the barriers have side walls and the phosphor layers extend to and almost entirely cover the side walls of the barriers; the address electrodes exist on a side of the substrate opposite to the display electrodes and the address electrodes are entirely covered with the phosphor layers; the device further comprises a substrate and a underlying layer of a low melting point glass containing a light color colorant formed on the substrate and the address electrodes are formed on the underlying layer; at least part of the barriers comprises a low melting point glass containing a light color colorant; and the barriers comprise a low melting point glass containing a dark color colorant in a top portion thereof and a low melting point glass admixed with a light color colorant in the other portion.
In accordance with the present invention, there is also provided a process for manufacturing a full color surface discharge plasma display device as above, in which the address electrodes and the barriers are parallel to each other and the address electrodes comprise a main portion for display parallel to the barriers and a portion at an end of said main portion for connecting to outer leads, the process comprising the steps of printing a material for forming the main portions of the address electrodes using a printing mask, printing a material for forming the outer lead-connecting portions, and printing a material for forming the barriers using the printing mask used for printing the material for forming the main portions of the address electrodes.
Further, there is also provided a process for manufacturing a full color surface discharge type plasma display device as above. This process comprises the steps of forming the barriers on the second substrate, almost filling gaps between the barriers above the second substrate with a phosphor paste, firing the phosphor paste to reduce the volume of the phosphor paste and form recesses between the barriers and to form a phosphor layer covering almost the entire surfaces of side walls of the barriers and covering surfaces of the second substrate between the barriers.
It is preferred that the phosphor paste comprise 10 to 50% by weight of a phosphor and the filling of the phosphor paste be performed by screen printing the phosphor paste into the spaces with a square squeezer at a set angle of 70 to 85 degrees.